Digestion & Absorption Flashcards
3 conditions of the gastric stomach environment that enable chemical and physical digestion are
• Acidic/low pH
• Enzymes secreted for protein digestion
•churning to mix contents
State the 2 main roles of bile in digestiom
• To neutralise stomach acid (by being alkaline)
• To emulsify fats
Where does lipase action take
Place
•Lumen of the small intestine
Explain emulsify
• Breaking fat droplets down into smaller droplets
*increases SA
How are villi adapted
What process do fatty acids and glycerol enter the epithelial cell by
•Simple diffusiom
Explain the advantages of lipid droplet and micelle formation
Droplets increase surface areas (for lipase / enzyme action);
(So) faster hydrolysis / digestion (of triglycerides / lipids);
Micelles carry fatty acids and glycerol / monoglycerides to / through membrane / to (intestinal epithelial) cell;
Increase in toxic lipid content in blood
Increases the risk of atheroma
Which leads to blockage in coronary arteries, increasing the risk of blood clots in the coronary arteries
Describe how proteins are digested in the human gut.
- Hydrolysis of peptide bonds;
- Endopeptidases break polypeptides into smaller peptide chains;
- Exopeptidases remove terminal amino acids;
- Dipeptidases hydrolyse / break down dipeptides into amino acids;
Why can only monomers be transported across the epithelial cell membrane
Because they are small enough and complementary to the binding sites of specific carrier proteins that move specifically complementary monomers across the epithelial cell membrane
Describe how glucose is absorbed from the ilium into the blood
Na* are actively transported out of the epithelial cell into the blood (by sodium potassium pump)
Creates a conc gradient of Na+ between the lumen of the ilium and the epithelial cell
Co transporter proteins have 2 binding sites which are complementary to both Na* and glucose. Only when both molecules bind will they be moved across the membrane
Na+ and glucose enter by facilitated diffusion using complementary Co transporter proteins
Na* diffuse into cell down conc gradient
Glucose moves into cell against conc gradient
Glucose Moves into blood vja facilitated diffusion
*ATP NOT REQUIRES WEN MOVING AGAINST CONC GRADIENT
Where does lipid digestion take place
Lumen of the ileum
Endopeptidases
Hydrolyse internal peptide bonds
Producing more ends which increases the SA
Faster hydrolysis
Test for starch
Add potassium iodide solution
Blue black colour indicates starch
Bile salts
Theyre mixed with lipid droplets to form smaller droplets (emulsified)
Which increases SA for faster hydrolysis by lipase
Bile salts glycerol and fatty acids also form micelles
Golgi apparatus in lipid digestion and absorption
Modifies triglycerides
Combines triglycerides with proteins (lipoproteins)
Forms vesicles
What enzymes does pancreas include
Pancreatic amylase lipase exopeptidases
What enzymes does the ileum contain
Membrane bound dipeptidases and disaccharides
What enzymes does stomach contain
Endopeptidases (pepsin) + exopeptidases
Describe and explain 2 features you would expect to find in a cell specialised for absorption
Folded membrane/microvilli so larger SA
Large number of carrier proteins for AT
Large number of mitochondria to release energy for AT
Membrane bound enzymes maintain conc gradienr
Golgi apparatus in digestion
Modifies triglycerides
Combines with proteins then releases -exocytosis
Forms vesicles
Describe processes involved in absorption and transport of lipid molecukes
Micelles contain bile salts+fatty acids+monogycerides
Micelles make fatty acids soluble in water
Fatty acids absorbed by diffusion
Triglycerides reformed in cells (Golgi apparatus)
Exocytosis
Wat does lipase hydrolyse glycerol into
Fatty acids+monoglycerides
